Was the doomed US submarine caught in a monstrous whirlpool in the South China Sea? (to update)

It’s the stuff of science fiction. A giant whirlpool, stretching hundreds of miles, suddenly appears in the ocean, threatening anything in its path.

But now, following the declassification of a Chinese operation, it appears this particular maelstrom was all too real. And it could be the explanation behind an international incident involving an American nuclear-powered submarine.

In September 2021, China launched a massive operation to hunt and record a huge whirlpool, more than 200 km (124 miles) in diameter, that appeared east of the Paracel Islands in the South China Sea.

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China’s most advanced research vessel and largest fleet of drones ever assembled were sent to carry out comprehensive tracking of this vortex in the air, on the sea surface and underwater.

Around the same time, the USS Connecticut, a Seawolf-class nuclear-powered fast attack submarine operated by the U.S. Navy, was also in the area.

On October 2, 2021, it hit an unknown object and had to make an emergency breach. It suffered serious damage, with repairs ongoing to this day.

A US military investigation blamed the negligence of the officers and crew on board, as well as their lack of knowledge of the terrain.

Now, on the third anniversary of the incident, the Chinese government has declassified its whirlpool hunting operation, with the scientific data collected at the time published last month in the Chinese academic journal Scientia Sinica Terrae.

It remains unclear whether there is a link between the US submarine collision and the whirlpool. Scientists involved in the project declined to comment on the matter.

The operation to track the Chinese drone fleet began on September 15, 2021 and continued until September 22. When the tracking was complete, the whirlpool remained extremely powerful. Based on past experience, the scientists wrote, such phenomena “may last weeks to months.”

The collision occurred just 10 days later, on October 2. The Connecticut’s hull suffered severe damage but did not completely lose power, according to the U.S. Navy.

A satellite image taken on October 3 showed the submarine floating on the ocean surface, 42.8 nautical miles southeast of the Paracel Islands, also known as the Xisha Islands in China, slowly sailing south.

The satellite image was released by the South China Sea Strategic Situation Probing Initiative (SCSPI), an open-source intelligence organization based in Beijing.

The submarine’s coordinates were 15.5 degrees north and 113 degrees east, according to SCSPI.

The graphs in the scientific article show that this location was still within the whirlpool’s range of influence, about 30 nautical miles from the navigation path of one of the Chinese unmanned vessels that patrolled the area a few days earlier.

This type of eddy is also known as a mesoscale eddy. In the 1930s, American oceanographer Columbus O’Donnell Iselin first discovered and recorded this phenomenon during a trip from New York to Bermuda.

Mesoscale eddies often appear like ghosts, containing incredible amounts of energy within them. According to an estimate by some scientists, these rotating masses of water can carry more than 90% of the kinetic energy of the planet’s surface.

These disturbances in seawater can reduce sonar accuracy, posing a threat to the safe navigation of submarines.

They can also interfere with the propagation of electromagnetic waves in the atmosphere through air-sea interactions, leading to communications disruptions and even causing aircraft to disappear from radar screens.

Due to the lack of complete observational data, the exact causes of these eddies still remain largely unknown.

By studying the 2021 South China Sea whirlpool, Chinese scientists discovered an exceptionally complex structure within it.

At the center of the whirlpool, about 50 to 150 meters (164 to 492 feet) below the sea surface, the drone fleet found a high-temperature core; closer to the sea surface, they found a low-temperature core; and at a depth of 200 meters (656 feet), they discovered another high-temperature core.

A large amount of seawater rotates clockwise around these cores at a speed of about 0.4 meters per second. Although this speed may seem slow, a submarine may encounter dramatic changes in seawater temperature and density as it crosses this area.

The difference in heat between adjacent bodies of water within the whirlpool, for example, can reach four times, according to data collected by Chinese drones.

These changes are so intense and sudden that some drones, when moving from one layer of water to another, suffered unexpected impacts and lost their data collection capacity for a period of time.

The fleet of drones also detected waveguides suspended at an altitude of about 600 meters (1,968 feet) above the ocean surface. This abnormal atmospheric phenomenon can seriously affect the quality of wireless communication and the normal operation of the radar.

A variety of smart equipment was used in the operation, including unmanned vessels, gliders, fixed-wing and rotary-wing drones. Among them, large fixed-wing drones were responsible for communication and coordination between the various unmanned platforms.

China’s BeiDou Satellite Network and other space infrastructure also participated in the operation.

China is currently the only country capable of tracking suddenly appearing whirlpools using large numbers of drones. According to the newspaper, similar operations are expected in the future and their scale could be even larger.

The scientists involved in the operation came mainly from the Chinese Academy of Sciences, Sun Yat-sen University and Nanjing University of Information Science and Technology, the latter having close ties with the military meteorological department of the People’s Liberation Army (PLA).

The Seawolf class is the most advanced nuclear attack submarine currently in service with the U.S. Navy, known for its high speed, quietness and excellent environmental sensing capabilities.

The US Navy conducted an investigation into the 2021 incident and concluded that the submarine collided at extremely high speed with an undersea mountain that did not appear on any maps. The incident was attributed to preventable human error.

“No action or inaction caused this accident, but it was preventable,” said an investigation report released in 2022.

Following the collision, Commander Cameron Aljilani, his second in command, Lieutenant Commander Patrick Cashin, and chief sonar technician Cory Rodgers were removed from their posts “due to loss of confidence”.

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